Calamus is a plant mentioned several times in the Bible. In most cases, it is mentioned in the context of being a fragrant plant or one used in making incense. There is probably no connection between calamus and marijuana.
Exodus 30:23 says, “Take the following fine spices: 500 shekels of liquid myrrh, half as much (that is, 250 shekels) of fragrant cinnamon, 250 shekels of fragrant calamus.” (This is referring to the recipe for the anointing oil used for the priests.)
Calamus is mentioned in Song of Solomon 4:12–14 in the context of praising the bride’s charms: “You are a garden locked up, my sister, my bride; you are a spring enclosed, a sealed fountain. Your plants are an orchard of pomegranates with choice fruits, with henna and nard, nard and saffron, calamus and cinnamon, with every kind of incense tree, with myrrh and aloes and all the finest spices.”
God’s complaint against Israel in Isaiah 43:24 also mentions calamus: “You have not bought any fragrant calamus for me, or lavished on me the fat of your sacrifices. But you have burdened me with your sins and wearied me with your offenses.” (KJV translates the word for the plant as “sweet cane” here.)
Jeremiah 6:20 has another reference to calamus: “What do I care about incense from Sheba or sweet calamus from a distant land? Your burnt offerings are not acceptable; your sacrifices do not please me.” (Again, the KJV translates the word as “sweet cane.” The ESV has “frankincense.”)
According to Ezekiel 27:18–19, Tyre produced calamus as an export: “Damascus did business with you because of your many products and great wealth of goods. They offered wine from Helbon, wool from Zahar and casks of wine from Izal in exchange for your wares: wrought iron, cassia and calamus.”
The word translated “calamus” in the Old Testament is a Hebrew word that is used for “cane” or “reed.” While it is often difficult to equate an ancient plant with a modern one, marijuana could hardly be described as a cane or reed, so the equivalence is unlikely. Today, essential oil of the cannabis flower can be used in fragrance, but the rest of the plant is not especially aromatic, so, once again, the equivalence seems unlikely.
Various other plants have been linked to the Bible’s calamus, including sweet flag (Acorus calamus).